// 计算响应头的中间件
module.exports = async (ctx,next) =>{
    const contentType = "application/json,charset=utf-8"
    ctx.set('Content-Type',contentType)
    ctx.set('Access-Control-Allow-Origin','*')
    ctx.set('Access-Control-Allow-Methods','OPTIONS,GET,PUT,POST,DELETE')
    await next()
}